A two-stroke engine is disclosed in U.S. Pat. No. 5,901,673 wherein fuel is injected into the combustion chamber in the region of bottom dead center with each rotation of the crankshaft and the air/fuel mixture, which forms in the combustion chamber, is ignited in the region of top dead center of the piston.
Defective ignitions occur during idle of the two-stroke engine because of the flow conditions and the low pressure and the high residual gas components so that the mixture is not combusted in the combustion chamber. The uncombusted mixture flows out of the combustion chamber during the downward stroke of the piston. This leads to the situation that the exhaust-gas values of the two-stroke engine greatly increase. It has been shown that, during idle, no clean scavenging of the combustion chamber takes place so that, at idle, exhaust gases, substantially fuel-free air and fresh mixture hardly mix in the combustion chamber. This can lead to the situation that the ignition spark ignites at a spatial distance to the mixture because of the spatial arrangement of the exhaust gas and the fresh mixture so that no or only an incomplete combustion takes place. This operation occurs at an irregular sequence and leads to the typical idle performance of a two-stroke engine.